The present invention relates to the geometric configuration of a flow-conducting component as well as the production of a such component.
Flow-conducting components are known in various embodiments. Depending upon operating conditions, that is to say operating pressure, conveying medium, medium temperature or the like, the component is manufactured from specific materials. The static construction of the housing is likewise greatly dependent upon the field of use.
At sections which are particularly loaded and above all at the transitions between different sections, in particular mechanical stresses can be built up which lead to shortening of the service lives. Stresses can be substantially reduced by an advantageous configuration of the notch, but this necessitates processing of the transition section with tools.
European patent publication no. EP 1 785 590 A1 shows the configuration and production of an impeller of a pump or turbine, wherein attention is focused in particular on the design of the notches. The impeller is welded in a plurality of locations, wherein stresses are directly prevented. During production, the procedure necessitates access to the notches with corresponding tools.
Both casting technology and also joining technology quickly reach the limits for flow-conducting components, since in some instances the notches are accessible only with difficulty and/or are not directly accessible at all from the exterior. This leads to considerable restrictions in the configuration of the geometry of the component.
The object of the invention is to find and to apply, for the mechanical loading at the transition points of a flow-conducting component, especially in the region of the notches, a geometric configuration which can be produced simply and cost-effectively.
The solution provides that the load spectrum of the notch is determined based on calculations, forming the notches geometrically according to their mechanical load, in particular where they are accessible only with difficulty and/or are not directly accessible at all from the exterior.
In this case it is advantageous that the design of the flow-conducting part, which may for example be an impeller for a centrifugal pump, can be free from the restriction of conventional requirements. Limitations due to casting technology and/or joining processes do not have to be taken into consideration, since only the mechanical and hydraulic properties are significant. Such freedom from traditional design principles enables a completely new configuration of the impeller.
In a further embodiment, in the flow-conducting component the notch is configured so that a transition in the component from a first section A to a second section B encloses an angle α. The angle bisector of the angle α is ascertained, wherein along this angle bisector a point P is determined. In each case a perpendicular of one of the arms (A, B) forming the angle α passes through the point P. Through the point P a straight line is applied to the respective perpendicular with an angle of 45°, wherein by the intersection of these straight lines with the respective arms (A, B) in each case a distance (S, S′) is fixed. The respective centers fix the points Q, Q′, wherein at the points Q, Q′ in each case straight lines are applied with an angle of 22.5° to the distances S, S′, intersecting the arms (A, B) in the points R, R′. The envelope E, E′ of this structure predetermines the geometric configuration of the notch.
This simple construction method makes it possible very simply to determine a geometry which in a direction-dependent manner takes into account the differential mechanical load in the component. Impinging forces are analyzed under the effect of the conveyed medium and the operating conditions provided, wherein minimum and maximum values are determined. According to these values the mechanical stability required for the impeller is determined. The method of calculation predetermines the geometric configuration and thus also the use of material and the machining of workpieces.
In an advantageous embodiment the flow-conducting component is produced by a generative process, wherein in particular metal powders are joined to form a component by a beam melting process such as for example laser or electron beam melting. This has the advantage that the impeller can be produced very simply and nevertheless in a very stable manner. Said processes enable the production of fluid-tight components with the possibility of substantial details. In this process a special surface structure can be additionally applied to the components, for example a shark skin which additionally improves the mechanical and hydraulic properties.
In a further advantageous embodiment, in the flow-conducting component at least one notch is arranged in the interior of the component, in particular in a cavity and/or an undercut. This has the advantage that in the geometric configuration of the component locations can be advantageously formed which are not accessible for the mechanical post-processing. This detailed configuration enables the production of components which are mechanically more resilient with a reduced use of material.
In a further embodiment the flow-conducting component is a pump component, in particular of a centrifugal pump. The geometric configuration is advantageous in particular in the case of impellers and/or guide wheels of centrifugal pumps. These parts are subjected to particularly high mechanical loads. The transitions between a guide/impeller vane and a cover disc are sometimes accessible with great difficulty. In a centrifugal pump, in addition to the purely geometric overall structure the surfaces of the individual impeller vanes can of course also be freely configured, so that the boundary layer between the impeller and the fluid can be influenced. In the case of inducers it is also possible inter alia to make components hollow, so that considerable savings of material are possible. The component must then obtain its mechanical stability through the corresponding configuration of the struts inside the hollow spaces, as well as the transitions between mechanically stabilizing sections according to the above design rule.
In a further advantageous embodiment the component is produced from an iron-based material. This enables a simple and cost-effective production on tools which are already ready for mass production. The iron-based material is advantageously an austenitic or martensitic or ferritic or duplex material. This enables the production of corrosion-resistant components. The production of the powders required for the aforementioned high-energy beam processes is likewise cost-effective and simple. This is even more apparent if the iron-based material is advantageously a gray or spheroidal graphite iron material.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.